The most common and widely used high speed mail inserters are of the "Phillipsburg-type", having initially been introduced in the late 1920's. U.S. Pat. No. 2,325,455 discloses such a mail insertion device. These mail inserters typically include a plurality of "picking stations", each having a respective stack of sheet items, or mail inserts, and a picker arm. The picking stations are arranged in a row, partially overlying a conveyor. The picker arm includes a jaw at its lower end, adapted to grip a sheet, or insert, previously segregated from the stack. The picker arm is mounted for rotation about its upper end, and reciprocates from a first position, where the jaw grips an individual sheet, to a second position, where the jaw releases the sheet over the conveyor. The conveyor is successively indexed beneath each picking station, for collating the proper number and types of sheets, or mail inserts. After the sheets are properly assembled into an insert packet, the packet is transported to an insertion station, and inserted into an open envelope.
In addition to the aforementioned picking stations, conveyor, and insertion station, the "Phillipsburg-type" machines include numerous other sub-assemblies and components. These additional items are used for manipulating the stack of sheets, handling, preparing, and sealing the envelopes, and rejecting defectively inserted envelopes. Cams, chains, gears, drive shafts, and electromechanical switches are used to actuate and control, overall operation and timing of the machine. Each of the various stations, sub-assemblies, and components, must be timed to actuate in proper sequence, to prevent jamming, insertion faults, or envelope sealing faults.
Currently available inserter machines use numerous cams, located on a main drive shaft, as the principal means for drive and timing control. If the machine is running at low speeds, say 200 insertions per hour, the cams are set in a first position, or rotational angle, on the main drive shaft. If higher operational speeds are desired, a skilled operator or mechanic will manually advance and reset the rotational angle of the cams, to a second position. This requirement for mechanically repositioning the cams, and other components which require timing adjustments for different operational speeds, is time consuming and reduces throughput for the machine. And, sometimes, to avoid the readjustment process completely, an operator will simply leave the cams in a middle-range setting, which does not work in optimum fashion either for low or high speed operation.